I have to confirm that the camera behaves exactly as you have described when the AF activation is set to AF-ON only - I have checked the support database and it seems this issue has been raised already by other customers that rely on the focus trap technique in their work.
It is currently being investigated in Nikon Japan - unfortunately we do not receive any feedback in such cases. I will send your report to the relevant department as well. The best we can possibly hope for is future firmware update, however I cannot promise it will be taken into consideration by developers.
Donc Bug confirmé.... quant à la MAJ firmware : "c'est pas gagné" , mais ont-ils le choix ?
La pression monte... cherchez "trap focus issue d800" , et vous verrez , il y a du monde.